[Mojo][Kernels] Fix signature of adaptive function in Memset notebook…

… (#20919)

Should be the last notebook that uses `search`, and therefore the
adaptive function must have only position-only arguments.

modular-orig-commit: 2ea7ecfb598f312b49f517f9a2a26d28c4a809a2

examples/Memset.ipynb

@@ -16,6 +16,7 @@
       ]
     },
     {
+      "attachments": {},
       "cell_type": "markdown",
       "metadata": {},
       "source": [
@@ -675,7 +676,7 @@
       "outputs": [],
       "source": [
         "@adaptive\n",
-        "fn memset_autotune_impl(ptr: BufferPtrType, value: ValueType, count: Int):\n",
+        "fn memset_autotune_impl(ptr: BufferPtrType, value: ValueType, count: Int, /):\n",
         "    memset_impl_layer[-100, 100](ptr, value, count)"
       ]
     },